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Re: Summary Table Design Question
Posted by: Rick James
Date: July 26, 2015 08:36AM

It depends.

My rule of thumb is that a Summary Table should have one-tenth as many rows as the Fact table. (This, of course, can vary widely.) If Day+Company has half as many rows as the Fact table, it is not doing much summarization, and is probably not very efficient. If summarizing only on Day leads to a summary table with 1/1000 the rows, that's great for efficiency, but begs for adding another 'dimension'.

Always approach the Summary table with SUM(sums) and SUM(counts) -- That way a daily Summary table can handle a Weekly report (etc). And it would automatically handle your case of "multiple rows for each day".

Approaching your question from a different angle:
"save data for each country separately" -- It is much better to have a `country_code` column in a single table than having a hundred tables, one per country.

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Re: Summary Table Design Question
July 26, 2015 08:36AM
July 28, 2015 01:39PM

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